Tens of thousands of anti-fascists took to the streets of Boston and dwarfed a right wing rally, in an incredible repudiation of white nationalism a week after the Charlottesville bloodshed.

A right-wing Free Speech demonstration had been planned in the city, just one week after a neo-Nazi rally in Virginia saw a white supremacist plough his car into counter-protesters, killing a young woman.

Organisers of the Free Speech rally publicly distanced themselves from the neo-Nazis who fomented violence in Charlottesville, Virginia, on August 12.

But opponents feared that white nationalists would show up in Boston anyway, raising the spectre of ugly confrontations in the first potentially large and racially-charged gathering in a major US city since Charlottesville.

Some counter-protesters dressed entirely in black and wore scarves over their faces, as they chanted anti-Nazi and anti-fascism slogans.

Around 15,000 counterprotesters turned up in Boston (Picture: Reuters)

Boston Police officers react as a crowd of counter protesters clashes with them (Picture: Reuters)

TV cameras showed a group of counter-protesters on the Common chasing a man with a Trump campaign banner and cap, shouting and swearing at him.

However, other counter-protesters intervened and helped the man safely over a fence into the area where the conservative rally was to be staged.

The unrest comes just one week after bloodshed in Charlottesville (Picture: Getty Images)

Tensions in the US are high after a young woman was killed by a white supremacist in Charlottesville last week (Picture: Getty Images)

Counterprotesters had worried that white supremacists would turn up to the ‘free speech’ demonstration – although the organisers have publicly distanced themselves from the Unite the Right rally (Picture: Getty Images)

The permit issued for the rally on Boston Common came with severe restrictions, including a ban on backpacks, sticks, and anything that could be used as a weapon.

The Boston Free Speech Coalition, which organised the event, said it has nothing to do with white nationalism or racism and its group is not affiliated with the Charlottesville organisers in any way.

‘We are strictly about free speech,’ the group said on its Facebook page. ‘We denounce the politics of supremacy and violence.’